Ultrasound imaging system and method with automatic adjustment and/or multiple sample volumes

ABSTRACT

Adjustment of operation of an ultrasound imaging system may be based at least in part on one or more characteristics represented in ultrasound return signals from two or more sample volumes. Adjustment may include adjusting a principal sample volume location or selecting a new principal sample volume. For example, a location of a principal sample volume may be adjusted or new principal sample volume selected so as to remain focused on an identified region of interest or to maintain the principal sample volume relative to some structure or reference. The principal sample volume may be maintained in the center or along a centerline of an artery or other structure, as the transducer array is moved along the artery or structure.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/865,852, filed on Apr. 18, 2013, now U.S. Pat. No. 9,451,933, which acontinuation of U.S. patent application Ser. No. 12/773,665, filed onMay 4, 2010, now U.S. Pat. No. 8,439,840, which are hereby incorporatedby reference.

BACKGROUND

Technical Field

This application relates to ultrasound imaging systems, for instancemedical diagnostic ultrasound imaging systems and, in particular, to theuse of information contained in ultrasound return signals to operate theultrasound imaging system.

Description of the Related Art

Ultrasound imaging systems employ transducer arrays to produce andtransmit ultrasound pressure waves into an object such as a body, tissueor other material. The transducer arrays also receive ultrasound returnor echo signals and produce analog transducer element voltage signalswhich are induced at the transducer array by the received ultrasoundreturn or echo signals.

Many ultrasound imaging systems are capable of operating in variousmodes for sampling, processing and/or presenting ultrasound informationin a variety of useful representations. For example, ultrasound systemsmay employ A-, B-, M-, Doppler, energy, power, Doppler amplitude orcolor angio modes. Some ultrasound systems are capable of concurrentlydisplaying information in more than one type of representation.

A region in three-dimensional space from which data is collected iscommonly referred to as a sample volume. The sample volume typically hasa width determined by the lateral margins of the ultrasound beam and anaxial depth along the ultrasound beam determined by a duration of thetransmitted ultrasound pulse and a duration of a sample gate implementedby the circuitry of the ultrasound imaging system.

It is often desirable or even necessary to sample or image a desiredlocation (e.g., three-dimensional location, including axial depth) in amaterial. For instance, medical imaging typically involves capturing asample or image of a volume at a desired location in a body oranatomical structure (e.g., bodily organ). In some applications, asonographer or clinician may locate or place a sample volume withreference to a two-dimensional image (e.g., B-mode image), then switchthe ultrasound imaging system into “Doppler” mode to see the “Doppler”waveform.

However, it can be difficult to maintain the sample volume in a desiredlocation. Such may be difficult when there is no or relatively littlerelative movement between the transducer array and the desired location.Such may be even more difficult when there is relative movement betweenthe transducer array and the desired location, for instance where thetransducer array is translated along a tissue or structure such as alongan artery. If the ultrasound imaging system has “triple” mode capabilityor an Echo/Doppler mode, a sonographer or clinician may use a referenceto aid in manually maintaining a sample volume in a desired or correctlocation. However, such may adversely take away acquisition time formDoppler firings, which reduces the ability to view high flow rates.

New approaches that facilitate maintaining a sample volume at desiredlocations while allowing relatively high pulse repetition frequency(PRF) are desirable.

BRIEF SUMMARY

Systems and methods described herein adjust operation of an ultrasoundimaging system based at least in part on one or more characteristicsrepresented in ultrasound return signals from two or more samplevolumes. Such may maintain a sample volume focused at a desired locationor region of interest, for example centered with respect to someanatomical structure such as an artery. Such may facilitate ultrasoundimaging when there is no or little movement of the transducer relativeto the anatomical structure or when there is significant relativemovement therebetween.

Such may employ multiple sample volumes. For example, one sample volumemay be referred to as a principal sample volume. Other volumes around orproximate the principal sample volume may be sampled as well. The othervolumes may be referred to as additional sample volumes to distinguishfrom the principal sample volume. The additional sample volumes may beaxially and/or laterally disposed from the principal sample volume.While the principal sample volume may be locus or center of all samplevolumes, such is not necessary.

The principal and additional sample volumes may be evaluated fromtime-to-time to determine which of the sample volumes most closelycorresponds or correlates with a desired location. The sample volumewhich most closely corresponds or correlates with the desired locationmay become the next sample volume. The additional sample volumes may besimilarly updated. Such may be preformed automatically be the ultrasoundimaging system, for example without operator or user evaluation,selection or other intervention. Thus, for example, the system andmethods may adjust a principal sample volume location or select a newprincipal sample volume. For example, a location of a principal samplevolume may be adjusted or new principal sample volume selected so as toremain focused on an identified region of interest. Also for example, alocation of a principal sample volume may be adjusted or a new principalsample volume selected so as to maintain the principal sample volumerelative to some anatomical structure or some reference. For instance,the principal sample volume may be maintained in the center or along acenterline of an artery, as the transducer array is moved along theartery.

A method of operating an ultrasound imaging system may be summarized asincluding generating a first number of ultrasound pressure waves;receiving a first number of ultrasound return signals from a principalsample volume and at least one additional sample volume that have atleast respective portions thereof that are at least one of axiallydisplaced or laterally displaced with respect to one another in responseto the first number of ultrasound pressure waves; and adjusting by acontrol circuit at least one operational parameter of the ultrasoundimaging system based at least in part on at least one characteristicrepresented in the received first number of ultrasound return signals.The adjusting may be automatic, without intervention of an operator oruser.

Adjusting by a control circuit at least one operational parameter of theultrasound imaging system based at least in part on at least onecharacteristic represented in the received ultrasound return signals mayinclude selecting a new principal sample volume to be sampled; andselecting a number of additional sample volumes to be sampled that haveat least respective portions thereof that are at least one of axiallydisplaced or laterally displaced with respect to the new principalsample volume. Adjusting by a control circuit at least one operationalparameter of the ultrasound imaging system based at least in part on atleast one characteristic represented in the received ultrasound returnsignals may include generating a second number of ultrasound pressurewaves directed to the new principal sample volume and at least one ofthe additional sample volumes that have at least respective portionsthereof that are at least one of axially displaced or laterallydisplaced with respect to the current principal sample volume.

Adjusting by a control circuit at least one operational parameter of theultrasound imaging system based at least in part on at least onecharacteristic represented in the received ultrasound return signals mayinclude selecting a new principal sample volume to be sampled; andselecting at least two additional sample volumes to be sampled that haveat least respective portions thereof that are laterally opposed to oneanother across the new principal sample volume. Selecting a newprincipal sample volume may include selecting one of the principalsample volume or the at least one additional sample volume as the newprincipal sample volume.

Adjusting by a control circuit at least one operational parameter of theultrasound imaging system based at least in part on at least onecharacteristic represented in the received ultrasound return signals mayinclude selecting one of the principal sample volume or the at least oneadditional sample volume as a new principal sample volume to be sampled;and selecting at least two additional sample volumes to be sampled thathave at least respective portions thereof that are axially opposed toone another across the new principal sample volume.

The method of operating an ultrasound imaging system may further includebeam forming to sample a new principal sample volume; beam forming tosample at least two additional sample volumes that have at leastrespective portions thereof that are axially opposed to one anotheracross the new principal sample volume; and beam forming to sample atleast two additional sample volumes that have at least respectiveportions thereof that are laterally opposed to one another across thenew principal sample volume.

Generating a first number of ultrasound pressure waves may includetransmit beam forming to transmit at least one ultrasound pressure wavealong an initial principal axial ray; transmit beam forming to transmitat least one ultrasound pressure wave along an initial first lateralaxial ray laterally displaced from the initial principal axial ray; andtransmit beam forming to transmit at least one ultrasound pressure wavealong an initial second lateral axial ray laterally displaced from theinitial principal axial ray and the initial first lateral axial ray. Themethod of generating a first number of ultrasound pressure waves mayfurther include transmit beam forming to transmit at least oneultrasound pressure wave along a new principal axial ray; transmit beamforming to transmit at least one ultrasound pressure wave along a newfirst lateral axial ray laterally displaced from the new principal axialray; and transmit beam forming to transmit at least one ultrasoundpressure wave along a new second lateral axial ray laterally displacedfrom the new principal axial ray and the new first lateral axial ray.The method of generating a first number of ultrasound pressure waves mayfurther include transmit beam forming to transmit at least oneultrasound pressure wave along a new principal axial ray different fromthe initial principal axial array; transmit beam forming to transmit atleast one ultrasound pressure wave along a new first lateral axial raylaterally displaced from the new principal axial ray; and transmit beamforming to transmit at least one ultrasound pressure wave along a newsecond lateral axial ray laterally displaced from the new principalaxial ray and the new first lateral axial ray.

Generating a first number of ultrasound pressure waves may includetransmit beam forming to transmit the ultrasound pressure waves along atleast three axial rays, the three axial rays laterally spaced from oneanother.

Receiving a first number of ultrasound return signals from a principalsample volume and at least one additional sample volume may includereceive beam forming to receive ultrasound return signals in response tothe at least one ultrasound pressure wave transmitted along the initialprincipal axial ray; receive beam forming to receive ultrasound returnsignals in response to the at least one ultrasound pressure wavetransmitted along the initial first lateral axial ray; and receive beamforming to receive ultrasound return signals in response to the at leastone ultrasound pressure wave along the initial second lateral axial ray.

The method of operating an ultrasound imaging system may further includeevaluating the at least one characteristic represented in the receivedultrasound return signals upon which evaluation the adjusting at leastone operational parameter of the ultrasound imaging system is based.

Evaluating the at least one characteristic represented in the receivedultrasound return signals may include evaluating at least one valueindicative of at least one of a power, a variance, a velocity, or a setof echo data. Adjusting by a control circuit at least one operationalparameter of the ultrasound imaging system based at least in part on atleast one characteristic represented in the received ultrasound returnsignals may include selecting a new principal sample volume to at leastpartially coincide with a region of interest in an object being imaged;and selecting a number of additional sample volumes to be sampled thathave at least respective portions thereof that are at least one ofaxially displaced or laterally displaced with respect to the newprincipal sample volume. Adjusting by a control circuit at least oneoperational parameter of the ultrasound imaging system based at least inpart on at least one characteristic represented in the receivedultrasound return signals may include selecting a new principal samplevolume to be centered with respect to at least one structure of anobject being imaged; and selecting a number of additional sample volumesto be sampled that have at least respective portions thereof that are atleast one of axially displaced or laterally displaced with respect tothe new principal sample volume.

An ultrasound imaging system may be summarized as including at least onetransducer array; at least one control system including a number of beamformers communicatively coupled to the at least one transducer array andat least one controller communicatively coupled to the beam formers, thecontrol system configured to: generate a first number of ultrasoundpressure waves by the at least one transducer array; receive a firstnumber of ultrasound return signals via the at least one transducerarray, the first number of ultrasound return signals received from aprincipal sample volume and at least one additional sample volume thathave at least respective portions thereof that are at least one ofaxially displaced or laterally displaced with respect to one another inresponse to the first number of ultrasound pressure waves; and adjust atleast one operational parameter of the ultrasound imaging system basedat least in part on at least one characteristic represented in thereceived first number of ultrasound return signals; and at least onedisplay communicatively coupled to the control system to receive atleast image data therefrom for display of images on the display.Adjustment may be automatic, without the intervention of an operator oruser.

To adjust the at least one operational parameter of the ultrasoundimaging system based at least in part on at least one characteristicrepresented in the received ultrasound return signals, the controlcircuit may select a new principal sample volume to be sampled; andselect a number of additional sample volumes to be sampled that have atleast respective portions thereof that are at least one of axiallydisplaced or laterally displaced with respect to the new principalsample volume.

The control circuit may be further configured to: generate a secondnumber of ultrasound pressure waves directed to the new principal samplevolume and at least one of the additional sample volumes that have atleast respective portions thereof that are at least one of axiallydisplaced or laterally displaced with respect to the new principalsample volume.

To adjust the at least one operational parameter of the ultrasoundimaging system based at least in part on at least one characteristicrepresented in the received ultrasound return signals, the controlcircuit may select a new principal sample volume to be sampled; andselect at least two additional sample volumes to be sampled that have atleast respective portions thereof that are laterally opposed to oneanother across the new principal sample volume.

To adjust at least one operational parameter of the ultrasound imagingsystem based at least in part on at least one characteristic representedin the received ultrasound return signals, the control circuit mayselect one of the principal sample volume or the at least one additionalsample volume as a new principal sample volume; and select at least twoadditional sample volumes to be sampled that have at least respectiveportions thereof that are axially opposed to one another across the newprincipal sample volume.

To generate a first number of ultrasound pressure waves the controlcircuit may generate at least one ultrasound pressure wave along aninitial principal axial ray; generate at least one ultrasound pressurewave along an initial first lateral axial ray laterally displaced fromthe initial principal axial ray; and generate at least one ultrasoundpressure wave along an initial second lateral axial ray laterallydisplaced from the initial principal axial ray and the initial firstlateral axial ray. The control circuit may be further configured to:generate at least one ultrasound pressure wave along a new principalaxial ray; generate at least one ultrasound pressure wave along a newfirst lateral axial ray laterally displaced from the new principal axialray; and generate at least one ultrasound pressure wave along a newsecond lateral axial ray laterally displaced from the new principalaxial ray and the new first lateral axial. The control circuit may befurther configured to: generate at least one ultrasound pressure wavealong a new principal axial ray different from the initial principalaxial array; generate at least one ultrasound pressure wave along a newfirst lateral axial ray laterally displaced from the new principal axialray; and generate at least one ultrasound pressure wave along a newsecond lateral axial ray laterally displaced from the new principalaxial ray and the new first lateral axial ray.

The control circuit may be further configured to: evaluate at least onevalue indicative of at least one of a power, a variance, a velocity, orecho data as the at least one characteristic represented in the receivedultrasound return signals. To adjust at least one operational parameterof the ultrasound imaging system based at least in part on at least onecharacteristic represented in the received ultrasound return signals,the control circuit may select a new principal sample volume to besampled to at least partially coincide with a region of interest in anobject being imaged; and select a number of additional sample volumes tobe sampled that have at least respective portions thereof that are atleast one of axially displaced or laterally displaced with respect tothe new principal sample volume. To adjust at least one operationalparameter of the ultrasound imaging system based at least in part on atleast one characteristic represented in the received ultrasound returnsignals, the control circuit may select a new principal sample volume tobe sampled to be centered with respect to at least one structure of anobject being imaged; and select a number of additional sample volumes tobe sampled that have at least respective portions thereof that are atleast one of axially displaced or laterally displaced with respect tothe new principal sample volume.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not drawn to scale, and some of these elementsare arbitrarily enlarged and positioned to improve drawing legibility.Further, the particular shapes of the elements as drawn, are notintended to convey any information regarding the actual shape of theparticular elements, and have been solely selected for ease ofrecognition in the drawings.

FIG. 1 is a schematic diagram of an ultrasound imaging system accordingto one illustrated embodiment.

FIG. 2 is a schematic diagram of a transducer array transmittingultrasound pressure waves into a medium during a first period accordingto one illustrated embodiment, illustrating an initial principal samplevolume, a number of additional sample volumes axially disposed withrespect to the initial principal sample volume and a number ofadditional sample volumes laterally disposed with respect to the initialprincipal sample volume.

FIG. 3 is a schematic diagram of a transducer array transmittingultrasound pressure waves into a medium during a second period accordingto one illustrated embodiment, illustrating an new principal samplevolume axially displaced from the initial principal sample volume, anumber of additional sample volumes axially disposed with respect to thenew principal sample volume and a number of additional sample volumeslaterally disposed with respect to the new principal sample volume.

FIG. 4 is a schematic diagram of a transducer array transmittingultrasound pressure waves into a medium during a third period accordingto one illustrated embodiment, illustrating an new principal samplevolume laterally displaced from the initial principal sample volume, anumber of additional sample volumes axially disposed with respect to thenew principal sample volume and a number of additional sample volumeslaterally disposed with respect to the new principal sample volume.

FIG. 5 is a high level flow diagram of a method of operating anultrasound imaging system according to one illustrated embodiment whichincludes sampling at least two different sample volumes and adjusting atleast one operation parameter of the ultrasound imaging system based atleast in part on characteristics represented in received ultrasoundreturn signals.

FIG. 6 is a low level flow diagram of a method of adjusting at least oneoperation parameter of the ultrasound imaging system based at least inpart on characteristics represented in received ultrasound returnsignals according to one illustrated embodiment, in accordance with themethod of FIG. 5.

FIG. 7 is a low level flow diagram of a method of operating anultrasound imaging system according to one illustrated embodimentincluding beam forming to sample an initial principal sample volume andinitial additional sample volumes, and beam forming to sample newprincipal sample volume and new additional sample volumes, in accordancewith the method of FIG. 5.

FIG. 8 is an ultrasound image showing a structure and a region ofinterest according to one illustrated embodiment.

FIG. 9 is a high level flow diagram of a method of operating anultrasound imaging system according to one illustrated embodiment,including selecting a new principal sample volume with reference to aregion of interest, in accordance with the method of FIG. 5.

FIG. 10 is an ultrasound image showing a structure and a sample volumeas well as a spectral Doppler trace according to one illustratedembodiment.

FIG. 11 is a high level flow diagram of a method of operating anultrasound imaging system according to one illustrated embodiment,including selecting a new principal sample volume with reference to atleast one structure of an object being imaged, in accordance with themethod of FIG. 5.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedembodiments. However, one skilled in the relevant art will recognizethat embodiments may be practiced without one or more of these specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures associated with ultrasound imagingsystems, microprocessors, micro-controllers, application specificintegrated circuits, transducers and displays have not been shown ordescribed in detail to avoid unnecessarily obscuring descriptions of theembodiments.

Unless the context requires otherwise, throughout the specification andclaims which follow, the word “comprise” and variations thereof, suchas, “comprises” and “comprising” are to be construed in an open,inclusive sense, that is as “including, but not limited to.”

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. Thus, the appearances of the phrases “in one embodiment” or“in an embodiment” in various places throughout this specification arenot necessarily all referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics may be combined inany suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its broadest sense, that is as meaning “and/or”unless the content clearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theembodiments.

Systems and methods described herein adjust operation of an ultrasoundimaging system based at least in part on one or more characteristicsrepresented in ultrasound return signals from two or more samplevolumes. The adjustment may be automatic, without evaluation, selectionor other intervention or action of an human operator or user beyondstandard operations of selecting a mode and scanning.

As discussed in the Brief Summary section, the systems and methodsdescribed herein may maintain a sample volume focused at a desiredlocation or region of interest, for example centered with respect tosome anatomical structure.

During any given period, multiple sample volumes may be sampled. One ofthe sample volumes may be referred to as a principal sample volume,while others sample volumes axially and/or laterally disposed from theprincipal sample volume may be referred to as additional sample volumes,to distinguish such from the principal sample volume. For axially spacedsample volumes (i.e., at different depths) the same received ultrasoundreturn signals may be filtered for different sample volume depths,adding little or acceptable acquisition time. For laterally spacedsample volumes may employ multiline acquisition techniques that employadditional receive beamformers to acquire sample volumes laterallyspaced from the axis or ray of the principal sample volume.

From time-to-time the principal and additional sample volumes may beevaluated to determine which of the sample volumes most closelycorresponds or correlates with a desired location or region of interest.The sample volume which most closely corresponds or correlates with thedesired location may become the next sample volume and the additionalsample volumes may be updated accordingly. Such may assist in keeping ormaintaining the ultrasound sampling focused at a desired location, evenwhen there is relative movement between the transducer array and thematerial being imaged or sampled. The evaluation may be based on avariety of characteristics or criteria, for example anatomical structureas represented in echo data, or one or more values indicative of power,variance, and/or velocity.

Operation may, for example, include adjusting a principal sample volumelocation or selecting a new principal sample volume, as illustrated inFIGS. 2-7. For example, a location of a principal sample volume may beadjusted or new principal sample volume selected so as to remain focusedon an identified region of interest, such as illustrated in FIGS. 8 and9. Also for example, a location of principal sample volume may beadjusted or a new principal sample volume selected so as to maintain theprincipal sample volume relative to some structure. For instance, theprincipal sample volume may be maintained in the center or an artery, asthe transducer array is moved along the artery, such as illustrated inFIGS. 10 and 11. Hence, a number of sample volumes may be acquiredaround a reference or region or interest, and which sample volume isdisplayed may be adjusted based on criteria (e.g., power, variance,velocity, echo) for a specific mode.

FIG. 1 shows an ultrasound imaging system 100 according to oneillustrated embodiment.

The ultrasound imaging system 100 includes a transducer array 102, acontrol system 104 and a display 106. The transducer array 102, controlsystem 104 and display 106 are coupled by one or more communicationspaths or buses. For example, the transducer array 102, control system104 and display 106 may be coupled by one or more data buses,instructions buses, and/or power buses. Such paths or buses may take avariety of forms, including electrically conductive paths such as wiresor electrical cables, or optical paths such as fiber optical cable.

The transducer array 102 produces and transmits ultrasound waves (e.g.,pulse and/or continuous) into an object, such as a body, tissue or othermaterial. The transducer array 102 also receives ultrasound returnsignals (e.g., echoes) and produces corresponding analog return signals(e.g., transducer element voltage signals) which are induced at thetransducer array by the received ultrasound return signals. Thetransducer array 102 may take the form of a solid state device thatallows for electronic control capabilities, variable aperture, and whichprovides excellent image performance and high reliability. Thetransducer array 102 may take the form of either a flat linear array ora curved linear array of elements. A curved linear array may provide abroad sector scanning field. The geometric curvature of a curved lineararray may advantageously reduce steering delay requirements on abeamformer of the control system 104. Where the transducer array 102takes the form of a flat array, the beamformer functionality of thecontrol system 104 may be capable of producing sufficient delay to bothsteer and focus, for example operating the transducer elements of thetransducer array 102 as a phased array. There are a large variety ofother transducers and transducer array that may be employed. The claimsshould not be limited to any particular transducer or transducer array.Suitable transducer arrays 108 are commercially available from a varietyof manufacturers and/or suppliers.

The control system 104 may provide several advanced features includingsynthetic aperture formation, frequency compounding, PW Doppler, colorpower, color flow (i.e., color velocity) and/or speckle reduction. Thecontrol system 104 may be capable of operating in A-, B-, M-, Doppler,energy, power, Doppler amplitude, color angio, or any other modes. Thecontrol system 104 may be capable of concurrently displaying informationin more than one type of representation (e.g., triple or Echo/Dopplermodes). The control system 104 may include a number of subsystems. Forexample, the control system 104 may include a transmit/receive subsystem108, a transmit beamformer subsystem 110, a receive beamformer subsystem112, a control subsystem 114, and a power subsystem 116.

The transmit/receive subsystem 108 may include one or moretransmit/receive switches 108 a (only one called out in FIG. 1) andoptionally one or more matching networks (not illustrated). Thetransmit/receive subsystem 108 is communicatively coupled to thetransducer elements of the transducer array 102. The transmit/receiveswitches 108 a isolate the functions of transmission and reception. Inparticular, the transmit/receive switches 108 a allow the elements ofthe transducer array 102 be selectively driven or to selectively receiverepresentations of ultrasound return signals in the form of analogtransducer element voltage signals or analog return signals. Thetransmit/receive subsystem 108 may be formed as a distinct ASIC. U.S.Pat. No. 5,893,363 titled ULTRASONIC ARRAY TRANSDUCER TRANSCEIVER FOR AHANDHELD ULTRASONIC DIAGNOSTIC INSTRUMENT describes such atransmit/receive ASIC. The transmit/receive ASIC may be positionedproximate the transducer array 102, for example within inches of theelements of the transducer array 102 to ensure short communicationspath.

The transmit beamformer subsystem 110 and receive beamformer subsystem112 include transmit and timing control circuitry or implements transmitand timing control functionality, providing control signals to thetransmit/receive subsystem 108 to control transmit waveform timing,aperture and focusing of the ultrasound pressure waves or beam. Eachbeamformer subsystem 110, 112 is discussed in more detail below.

The transmit beamformer subsystem 110 forms beams and drives thetransducer elements of the transducer array 102 via the transmit/receiveswitches 108 a. In particular, the transmit beamformer subsystem 110 mayinclude one or more sets of modulators 118 and/or delay circuitry 120.The modulator(s) 118 may be controlled to generate digital drivesignals, while the delay circuitry 120 may be controlled to delay thedigital drive signals, for instance to allow steering and/or focusing ofthe ultrasound pressure waves transmitted from the transducer array 102.Notably, multiple pairs of modulators 118 and delay circuitry 120 may beemployed. The transmit beamformer subsystem 110 may also include a oneor more sets of digital-to-analog converters (DACs) 122 and amplifiers124. The DACs 122 convert digital drive signals into an analog form,while the amplifiers 124 amplify the analog drive signals to providehigh-voltage waveforms used to drive the transducer elements of thetransducer array 102. Notably, multiple pairs of DACs 122 and amplifiers124 may be employed. Additionally, the transmit beamformer subsystem 110may also include one or more local processors, for instance localdigital processor(s) 126. The local digital processor(s) 126 may takethe form of digital signal processors (DSPs), application specificintegrated circuits (ASICs), programmable (PGAs), microprocessors and/orother integrated devices as well as discrete devices or circuits. Thelocal digital processor(s) 126 may be communicatively coupled to one ormore of the other components of the transmit beamformer subsystem 110,as well as communicatively coupled to the central control subsystem 114.Multiple transmit beamformers or components thereof may advantageouslyallow the imaging system to successively acquire samples from multiplesample volumes.

The receive beamformer subsystem 112 beam forms the analog signalsreceived from the individual transducer elements of the transducer array102, received via the transmit/receive switches 108 a, for example intoa coherent scanline signal. In particular, receive beamformer subsystem112 may include a one or more sets of amplifiers 128 andanalog-to-digital converters (ADCs) 130. The amplifiers 128 amplify theanalog signals (e.g., analog transducer element voltage signals), whilethe ADCs 130 convert the amplified analog signals into a digital form.For example, the amplifier(s) 128 may perform time gain compensation(i.e., TGC) to compensate for attenuation of ultrasound with depth.Notably, multiple pairs of amplifiers 128 and DACs 130 may be employed.The receive beamformer subsystem 112 may include one or more sets ofapodization circuitry 132, interpolation circuitry 134, as well as delaycircuitry 136. The apodization circuitry 132 may be used to accommodatefor side lobes, for instance by decreasing relative sensitivity near theends of a receiving surface of the transducer element(s). Additionally,or alternatively, relative excitation may be decreased if accommodatedfor via the transmit beamformer subsystem 110. The interpolationcircuitry 134 may be used to perform interpolation, for instance toallow a change in sampling rate. The delay circuitry 136 may becontrolled to delay various channels. Notably, multiple sets ofapodization circuitry 132, interpolation circuitry 134, as well as delaycircuitry 136 may be employed. The receive beamformer subsystem 112 mayalso include one or more local processors 138, for instance localdigital processors. The local digital processor(s) 138 may take the formof DSPs, ASICs, PGAs, microprocessors and/or other integrated devices.The local digital processor(s) 138 may be communicatively coupled to oneor more of the other components of the receive beamformer subsystem 112,as well as communicatively coupled to the central control subsystem 114.Additionally, the receive beamformer subsystem 112 may also include oneor more summers or summer circuits 140 which sums the digitized returnsignals of the various channels.

While not specifically illustrated, the receive beamformer subsystem 112may also include one or more filters or such may be implemented by oneor more local digital processors 138. Thus, the receive beamformersubsystem 112 may filter the scanline signals, amplify the scanlinesignals, and/or processes the filtered scanline signals as B modesignals, Doppler signals, or both. Multiple receive beamformers and/orfilters or components thereof may advantageously allow the imagingsystem to concurrently acquire samples from multiple sample volumes.

Normal sample volumes are typically one wavelength in duration. In someapplications, a single sample volume may be much longer than samplevolumes for conventional ultrasound imaging systems. In someapplications sample volumes may partially overlap adjacent samplevolumes. Thus, ultrasound imaging system described herein should haveenough filtering and computational power to timely process multiple longsample volumes.

The control subsystem 114 may include a central controller 142, one ormore memories or computer- or processor-readable storage mediums 144,and one or more buses 146 that couple the central controller 142 and thecomputer- or processor-readable storage mediums 144.

While illustrated as a single microprocessor, the central controller 142may take the form of one or more microprocessors (e.g., ReducedInstruction Set or RISC processor), DSPs, PGAs or ASICs. The centralcontroller 142 may execute instructions and/or program data stored onone or more computer- or processor-readable storage mediums 144, forexample a program memory. The central controller 142 is communicativelycoupled to the transmit beamformer subsystem 110 and receive beamformersubsystem 112 to control and synchronize the processing and controlfunctions throughout the ultrasound imaging system 100. For example, thecentral controller 142 may coordinate process timing and loading ofbuffers and registers with the data necessary to perform the processingand display requested by the user. Timing for the central controller 142may be provided by clock signals from the clock generator (not shown).It is to be recognized that the embodiments discussed herein areillustrative of only some of the possible embodiments. For example, theprocessing may be implemented in other ways and the processor(s) orother circuitry may be distributed in other manners or locations. Forinstance, a distributed architecture may be employed with communicationsoccurring over one or more buses, networks or other communicationsmediums.

The computer- or processor-readable storage mediums 144 may take avariety of forms. For example, the computer- or processor-readablestorage mediums 144 may include one or more Read Only Memories (ROM) 144a, Random Access Memories (RAM) 144 b, or other volatile or non-volatilestorage mediums such as FLASH memory, a magnetic disk (i.e., hard diskand drive), optical disk, etc. 144 c. The computer- orprocessor-readable storage medium 144 may store data used by thetransmit beamformer subsystem 110 or data produced by the receivebeamformer subsystem 112.

The control subsystem 104 may further include a set of user controls146. The display 106 and user controls 146 may form all or part of auser interface. The user controls 146 may allow a user to turn theultrasound imaging system 100 ON and OFF, enter time, date, and/orpatient data, interact with a graphical user interface that includesuser selectable icons or elements of a menu (e.g., pull down menu, popupmenu), and/or select or set various operating characteristics such as anoperating mode (e.g., B mode, Doppler), color Doppler sector or framerate, and special functions.

The central controller 142 is operated under user control by commands,selections and/or entries made by the user via the user controls 146. Asdescribed above, the user controls 146 allow a user to direct andcontrol the operations of the ultrasound imaging system 100. Where ahandheld form factor is employed, a number of functions, such as patientdata entry, Cineloop® operation, and 3D review, may be operated throughmenu control provided via a graphical user interface. Such mayadvantageously minimize the number of keys, buttons or switches presenton a small handheld housing. Additionally, or alternatively, a number ofoperational functions may be programmed to be logically associated withspecific diagnostic applications. Such operational functions may beautomatically executed or performed when a specific operating mode orapplication is selected by a user. For example, selection of B modeimaging may automatically invoke frequency compounding and depthdependent filtering, while selection of Doppler operation may causeautomatic set up of a four multiplier filter as a wall filter. The menuselection of specific clinical applications can, for example,automatically invoke specific feature settings such as TGC controlcharacteristics and focal zones.

The central controller 142 and possibly other controllers or circuitryreceives the ultrasound B mode and Doppler information from the receivebeamformer subsystem 112. The central controller 142 and possibly othercontrollers or circuitry may perform a scan conversion that producesvideo output signals or frames of video. The central controller 142 andpossibly other controllers or circuitry may be configured to addalphanumeric information to the video or other image data, such as thetime and/or date via a time and/or date function, and patientidentification. An optional graphics processor (not shown) may overlaythe ultrasound images with information such as depth and focus markersand cursors. Frames of ultrasound images may be stored in a dedicatedvideo memory (not shown). Such may allow selected frames to be recalledand replayed, for instance in a live Cineloop® real-time sequence. Videoinformation may be available at a video output. The video informationmay be made available in a variety of formats, for instance NTSC and PALformats or RGB drive signals for the display 106 or other a videomonitor.

The control subsystem 104 may include one or more communicationsinterfaces 148 to which the central controller 142 may becommunicatively coupled. The communications interfaces 148 may take avariety of forms for instance a communications port (e.g., UniversalSerial Bus or USB port, Ethernet port, FIREWIRE® port, infraredtransmitter/receiver). The communications interface 148 allows othermodules and functions to be communicatively coupled to or communicatewith the ultrasound imaging system 100. The communications interface 148can communicatively couple to a modem or communications link to transmitand receive ultrasound images, ultrasound information and/or otherinformation from remote locations. The communications interface 148 canaccept other data storage devices to add new functionality to theultrasound device, for instance an ultrasound information analysispackage. The communications interface 148 may also allow the centralcontroller 142 to access additional program instructions or data and/ortransmit image information remotely.

The ultrasound imaging system 100 may include a power subsystem 116 thatapplies power (e.g., battery power) to the other components andsubsystems of the ultrasound imaging system 100. For example, the powersubsystem 116 may monitor and control electrical power applied to thetransducer array 102, thereby controlling the acoustic energy which isapplied to the patient. The power subsystem 116 may also be configuredto minimize overall power consumption of the ultrasound imaging system100. The power subsystem 116 may provide electrical power from aportable power storage device (e.g., rechargeable battery cells,ultra-capacitor array, fuel cell array), particularly where theultrasound imaging system 100 takes the form of a handheld or portabledevice. The power subsystem 116 may include a DC-DC converter to convertthe low battery voltage to a higher voltage which is applied to thetransmit/receive subsystem 108 to drive the elements of the transducerarray 102. The power subsystem 116 may include a rectifier and step downconverter to convert AC power to recharge the power storage device(e.g., rechargeable battery cells, ultra-capacitor array).

The display 106 may take a variety of forms, for example a liquidcrystal display (LCD). The display 106 may be integrated into a commonhousing with the control system 104 and/or the transducer array 102, ormay be separate.

While the various components are generally described above as beinghoused in a single unitary or single piece housing, other alternativeswill be readily apparent from this description. For instance, some ofthe subsystems could be located in a common enclosure, with thebeamformer subsystems 110, 112 physically and/or communicativelydetachably coupled to the transducer elements of the transducer array102. This allows different transducer arrays to be used with a digitalbeamformer, digital filter, and image processor for various diagnosticimaging procedures. Alternatively, the transducer array 102,transmit/receive subsystem 108 and transmit and receive beamformersubsystems 110, 112 could be housed in a transducer housing, with thecontrol subsystem 104 including user controls 146 housed in a separatehousing along with the display 106. Various suitable structures andmethods are described in U.S. Pat. No. 7,604,596 and U.S. Pat. No.5,817,024. Other configurations of the ultrasound imaging system 100 maybe employed.

As previously discussed, ultrasound information may be used to adjustoperation of the ultrasound imaging system. For example, a focus ordirection of further ultrasound sample volumes may be adjusted. Forinstance, from time-to-time various sample volumes may be evaluated withrespect to a desired location (e.g., particular anatomical structure,reference, region of interest). Such may include a sample volume thatwas previously centered or best coincided with the desired location,such sample volume referred to as the principal sample volume. Such mayalso include other sample volumes axially and/or laterally disposed withrespect to the principal sample volume, referred to as additional samplevolumes. In response to the evaluation, a different sample volume may beidentified or selected as a new principal sample volume or the samesample volume may be reused as the principal sample volume. Likewise,the additional sample volumes may be updated or reused accordingly. Thismay be done by acquiring sample volumes in the lateral and/or axialdirections, without incurring significant increases in acquisition time,thus avoiding significant decreases in pulse repetition frequency (PRF)rates.

In particular, acquiring additional sample volumes at shallower depthsin the same axial direction as the principal sample volume can beachieved with incurring any additional “pings” or acquisition time,thereby having no effect on PRF rate, since the same sample data can beused and filtered for several different sample volume depths. Acquiringadditional sample volumes at deeper depths in the same axial directionas the principal sample volume will add a small amount of additionalacquisition time, but should not be so significant as to hinderoperation or substantially decrease temporal resolution.

The ultrasound imaging system 100 may employ conventional multilineacquisition techniques to acquire additional sample volumes in thelateral directions from the principal sample volume or principal axialray. To accomplish such, the ultrasound imaging system 100 mayadvantageously include multiple receive beamformers 112 to acquiresamples volumes to either side (e.g., left and right in FIGS. 2-4) of aprincipal axial ray. Multiple sample volumes may be acquired atdifferent axial depths along the additional axial rays laterallydisposed from the principal axial ray, in a fashion similar to that forthe principal axial ray.

FIGS. 2-4 illustrate various approaches to acquiring additional samplevolumes around a principal or main sample volume.

FIG. 2 shows a transducer array 200 transmitting ultrasound illustratedas axial rays extending into a medium during a first period, accordingto one illustrated embodiment. While illustrated in two-dimensions,those of ordinary skill in the art will appreciate that ultrasound imagesampling may take place in three-dimensions.

In particular, FIG. 2 shows an initial principal sample volume 202 thatis being sampled, at a first axial depth along an initial principalaxial ray 204. As illustrated in FIG. 2, a number of initial additionalsample volumes may be sampled at different axial depths along the sameinitial principal axial ray 204. These are illustrated as four initialadditional sample volumes 206 a-206 d (collectively 206), with pairs 206a, 206 d, 206 b, 206 c of these initial additional sample volumesaxially diametrically opposed to one another on either side of theinitial principal sample volume 202.

Also as illustrated in FIG. 2 a number of initial additional samplevolumes may be sampled, laterally disposed from the initial principalsample volume 202. These are illustrated as five initial sample volumes208 a-208 e (collectively 208) on a first lateral axial ray 210laterally disposed on one side of the initial principal axial ray 204,and five initial sample volumes 212 a-212 e (collectively 212) on asecond lateral axial ray 214 laterally disposed on the other side of theinitial principal axial ray 204. Pairs of the additional sample volumes208, 212 may be diametrically opposed from one another across respectiveones of the initial sample volumes 202, 206 on the principal axial ray204. As will be apparent from the teachings here to those of ordinaryskill in the art, greater or fewer sample volumes may be used.Additionally, or alternatively, the number of sample volumes on oneaxial ray may differ from the number of sample volumes on another axialray. As previously noted, ultrasound image sampling may take place inthree-dimensions. Hence additional sample volumes 206 may be arrayedabout the principal axis 204 at various angular locations. Thus, forexample a set of additionally sample volumes may be sampled in a planethat is orthogonal to the plane of the drawing sheet. Again, suchadditional samples in the orthogonal plane may be diametrically opposedwith respect to one another across the principal axial ray 204 or samplevolume 202.

FIG. 3 shows a transducer array 200 transmitting ultrasound illustratedas axial rays extending into a medium during a second period, accordingto one illustrated embodiment.

In particular, FIG. 3 shows a new principal sample volume 302 that isbeing sampled at a second axial depth along a principal axial ray 304.Notably, the second axial depth is different from the first axial depth(FIG. 2). As illustrated in FIG. 3, a number of new additional samplevolumes may be sampled at different axial depths along the same initialprincipal axial ray 304. These are illustrated as four new additionalsample volumes 306 a-306 d (collectively 306), with pairs of these newadditional sample volumes axially diametrically opposed to one anotheron either side of the new principal sample volume 302.

Also as illustrated in FIG. 3 a number of new additional sample volumesmay be sampled, laterally disposed from the new principal sample volume302. These are illustrated as five new sample volumes 308 a-308 e(collectively 308) on a first lateral axial ray 310 laterally disposedon one side of the principal axial ray 304, and five new sample volumes312 a-312 e (collectively 312) on a second lateral axial ray 314laterally disposed on the other side of the principal axial ray 304,diametrically opposed from one another across respective ones of the newsample volumes 302, 306 on the principal axial ray 304. Thus, a newprincipal sample volume 302 is sampled along with new additional samplevolumes 306, 308, 312 axially and/or laterally disposed with respect tothe new principal sample volume 302. As previously noted, greater orfewer sample volumes may be used and the number of sample volumes on oneaxial ray may differ from the number of sample volumes on another axialray. The comments regarding operation in a three-dimensional space madewith respect to FIG. 2 apply to this illustrated embodiment as well.

FIG. 4 shows a transducer array 200 transmitting ultrasound illustratedas axial rays extending into a medium during a third period, accordingto one illustrated embodiment.

In particular, FIG. 4 shows a new principal sample volume 402 that isbeing sampled at a new principal axial ray 404. Notably, the newprincipal axial ray 404 is different from the initial principal axialray 204 (FIG. 2). As illustrated in FIG. 4, a number of new additionalsample volumes may be sampled at different axial depths along the samenew principal axial ray 404. These are illustrated as four newadditional sample volumes 406 a-406 d (collectively 406), with pairs ofthese new additional sample volumes axially diametrically opposed to oneanother on either side of the new principal sample volume 402.

Also as illustrated in FIG. 4 a number of new additional sample volumesmay be sampled, laterally disposed from the new principal sample volume404. These are illustrated as five new sample volumes 408 a-408 e(collectively 408) on a first lateral axial ray 410 laterally disposedon one side of the new principal axial ray 404, and five new samplevolumes 412 a-412 e (collectively 412) on a second lateral axial ray 414laterally disposed on the other side of the new principal axial ray 404,diametrically opposed from one another across respective ones of the newsample volumes 402, 406 on the new principal axial ray 404.

Thus, a new principal sample volume 402 is sampled along with newadditional sample volumes 406, 408, 412 axially and/or laterallydisposed with respect to the new principal sample volume. As previouslynoted, greater or fewer sample volumes may be used and the number ofsample volumes on one axial ray may differ from the number of samplevolumes on another axial ray. The comments regarding operation in athree-dimensional space made with respect to FIG. 2 apply to thisillustrated embodiment as well.

FIG. 5 shows a method 500 of operating an ultrasound imaging system,according to one illustrated embodiment.

At 502, the ultrasound imaging system generates a first number ofultrasound pressure waves. For example, a transmit beamformer subsystemmay generate drive signals, causing one or more of the transducerelements of a transducer array to transmit ultrasound pressure waves. Aspreviously noted, these may be focused and/or directed. In particular,the ultrasound pressure waves may be generated to sample certain samplevolumes along one or more axial rays, at one or more axial depths.

At 504, the ultrasound imaging system receives a first number ofultrasound return signals for each of at least two sample volumes inresponse to the first number of ultrasound pressure waves. The twosample volumes have at least respective portions thereof that are atleast one of axially displaced and/or laterally displaced with respectto one another. For example, a receive beamformer subsystem may receiveand process analog signals produced by the transducer array in responseto ultrasound return signals.

At 506, the ultrasound imaging system evaluates at least onecharacteristic represented in the received ultrasound return signals.For example, the ultrasound imaging system may evaluate one or morevalues that are indicative of a power, a variance, a velocity, and/or aset of echo data. Such information may represent structures of interest,for example a vein or artery, bone, organ, flow of blood or other fluid,or may represent some other structure of interest. For instance, it maybe desirable to maintain the principal sample volume at least partiallycoincident with some defined region of interest (ROI). This may beparticularly desirable where there is some relative movement between thetransducer array and the object being sampled. For instance, it may bedesirable to maintain the principal sample volume coincident with somebodily structure where the transducer array is being moved, or thebodily structure moves or is being moved. Also for instance, it may bedesirable to maintain the principal sample volume along a centerline ofan artery, even where the artery is tortuous and/or the transducer arrayis being scanned along a body.

The characteristics, also referred to as parameters, may all be computedfrom the same acquired data or ultrasound information. As an example,velocity may be fastest in the center of a vessel. Thus, velocityinformation may be evaluated to determine the location of a centerlineof a vessel, and the principal sample volume moved or selected to becoincident, or at least partially coincident with the centerline asdetermined based on velocity. For instance, the measured or determinedvelocity may be compared to some threshold or to velocity measured ordetermined at other locations. In some instance, power may be a betterindicator of certain structure, such as the centerline of vesselcarrying blood or other fluid. Hence, the measured or determined powermay be compared to some threshold or to power measured or determined atother locations. In other instances, variance or some other measure ofturbulence may be suitable for indicating a location or presence of aparticular structure (e.g., blockage or plaque buildup). Hence, variancemay be evaluated against some threshold and/or against turbulence atother locations. Thus, the ultrasound imaging system should be capableof processing multiple sample volumes, as well as background echo data,from the same acquired ultrasound return signals. In addition, oralternatively, to evaluating characteristics such as power, a variance,a velocity, echo data may be computed for each axial ray. Using echoinformation and/or “Doppler” (e.g., pulse wave “Doppler”) informationmay allow locations of certain structures to be determined or computed.For example, the location of vessel walls may be determined or computedto aid in selecting which of the currently acquired sample volumes willbe the new principal sample volume (e.g., new center sample volume).Thus, for example, the new principal sample volume may be placedcoincident or at least partially coincident with a centerline of somestructure indicated by echoes alone, by one or more “Doppler”parameters, and/or a combination of echoes and “Doppler” parameters suchas velocity, power and/or variance. Thus, the ultrasound imaging systemshould be capable of processing multiple sample volumes, as well asbackground echo data, from the same acquired ultrasound return signals.The ultrasound imaging system may employ some of its transmissions(e.g., “pings”) to acquire two-dimensional ultrasound data and some ofits transmission to acquire Doppler ultrasound data. Thus, one ray maybe used to capture background image information (e.g., pulse echo) whileanother ray used to capture pulse wave Doppler information.

At 508, the ultrasound imaging system adjusts at least one operationalparameter based at least in part on at least one characteristicrepresented in the received first number of ultrasound return signals.The adjustment may be automatic or not. For example, the ultrasoundimaging system may adjust the transmit beamformer to move or change alocation of a principal sample volume. For instance, the ultrasoundimaging system may cause a new principal sample volume to be axiallydisplaced with respect to an initial or previous principal samplevolume. Alternatively or additionally, the ultrasound imaging system maycause a new principal sample volume to be laterally displaced withrespect to an initial or previous principal sample volume. Also forexample, the ultrasound imaging system may adjust the transmitbeamformer to move or change a location of an additional (i.e.,supplemental or not principal) sample volume. For instance, theultrasound imaging system may cause a new additional sample volume to beaxially displaced with respect to an initial or previous additionalsample volume. Alternatively or additionally, the ultrasound imagingsystem may cause a new additional sample volume to be laterallydisplaced with respect to an initial or previous additional samplevolume. Such may, for instance, move the principal sample volume to becentered with respect to some structure, such as an artery. Thus, whereone of the additional sample volumes is identified or selected as thenew principal sample volume, then the ultrasound transmissions from thetransducer array may be redirected and/or refocused to be centered onthe new principal sample volume.

FIG. 6 shows a method 600 of operating an ultrasound imaging system,according to one illustrated embodiment. The method 600 may, forexample, be executed as part of the method 500 (FIG. 5).

At 602, the ultrasound imaging system selects a new principal samplevolume to be sampled. For example, the ultrasound imaging system mayselect one of the at least two initial sample volumes as the newprincipal sample volume. Thus, for instance, one of the additionalsample volumes may meet a desired criteria (e.g., coincident or centeredwith respect to some region or interest, structure or reference), andhence will be used as the new principal sample volume. In someinstances, the previous principal sample volume may still meet thedesired criteria, and the same principal sample volume will be sampled.

Optionally, at 604, the ultrasound imaging system selects one or moreadditional sample volumes to be sampled. These additional sample volumeshave at least respective portions thereof that are at least axiallydisplaced with respect to the new principal sample volume. For example,the ultrasound imaging system may select at least two additional samplevolumes to be sampled that have at least respective portions thereofthat are axially opposed to one another across the new principal samplevolume. In some instances, the entire additional sample volumes will beaxially displaced from the entire principal sample volume.

Optionally, at 606, the ultrasound imaging system selects additionalsample volumes to be sampled that have at least respective portionsthereof that are at least laterally displaced with respect to the newprincipal sample volume. For example, the ultrasound imaging system mayselect at least two additional sample volumes to be sampled that have atleast respective portions thereof that are laterally opposed to oneanother across the new principal sample volume. In some instances, theentire additional sample volumes will be laterally displaced from theentire principal sample volume.

At 608, the ultrasound imaging system generates a second number ofultrasound pressure waves directed to the new principal sample volumeand at least one of the additional sample volume(s). The method 600 maythen repeat, substituting new principal and/or additional sample volumesfor initial or previous principal and/or additional sample volumes.

FIG. 7 shows a method 700 of operating an ultrasound imaging system,according to one illustrated embodiment. The method 700 may, forexample, be executed as part of the method 500 (FIG. 5).

At 702 a, the ultrasound imaging system transmit beam forms to transmitat least one ultrasound pressure wave along an initial principal axialray to sample an initial principal sample volume. For example, atransmit beamformer subsystem may produce drive signals to cause atransducer array to transmit ultrasound pressure waves along theprincipal axial array focused at a desired depth.

At 702 b, the ultrasound imaging system receive beam forms to receive atleast one ultrasound return or echo signal in response to the ultrasoundpressure wave transmitted along the initial principal axial ray tosample the initial principal sample volume. For example, a receivebeamformer subsystem may filter and otherwise process the ultrasoundreturn signals to produce image data and to determine information (e.g.,echo and/or “Doppler” characteristics or parameters) represented in theultrasound return signals, focused at one or more desired depths.

At 704 a, the ultrasound imaging system transmit beam forms to transmitat least one ultrasound pressure wave along an initial first lateralaxial ray laterally displaced from the initial principal axial ray. Forexample, a transmit beamformer subsystem may produce drive signals tocause a transducer array to transmit ultrasound pressure waves along anaxial ray laterally disposed with respect to the principal axial ray andfocused one or more desired depths.

At 704 b, the ultrasound imaging system receive beam forms to receive atleast one ultrasound return or echo signal in response to the ultrasoundpressure wave transmitted along the initial first lateral axial ray. Forexample, a receive beamformer subsystem may filter and otherwise processthe ultrasound return signals to produce image data and to determineinformation (e.g., echo and/or “Doppler” characteristics or parameters)represented in the ultrasound return signals, focused at one or moredesired depths.

At 706 a, the ultrasound imaging system transmit beam forms to transmitat least one ultrasound pressure wave along an initial second lateralaxial ray laterally displaced from the initial principal axial ray andthe initial first lateral axial ray. For example, a transmit beamformersubsystem may produce drive signals to cause a transducer array totransmit ultrasound pressure waves along an axial ray laterally disposedwith respect to the principal axial ray and focused one or more desireddepths.

At 706 b, the ultrasound imaging system receive beam forms to receive atleast one ultrasound return or echo signal in response to the ultrasoundpressure wave transmitted along the initial second lateral axial ray.For example, a receive beamformer subsystem may filter and otherwiseprocess the ultrasound return signals to produce image data and todetermine information (e.g., echo and/or “Doppler” characteristics orparameters) represented in the ultrasound return signals, focused at oneor more desired depths.

Thus, the ultrasound imaging system may, for example, sample at leasttwo additional sample volumes, laterally opposed to one another acrossthe initial principal sample volume.

At 708 a, the ultrasound imaging system transmit beam forms to transmitat least one ultrasound pressure wave along a new principal axial ray tosample a new principal sample volume. The new principal axial ray may bedifferent from the initial principal axial array.

At 708 b, the ultrasound imaging system receive beam forms to receive atleast one ultrasound return or echo signal in response to the ultrasoundpressure wave transmitted along the new principal axial ray to samplethe new principal sample volume. For example, a receive beamformersubsystem may filter and otherwise process the ultrasound return signalsto produce image data and to determine information (e.g., echo and/or“Doppler” characteristics or parameters) represented in the ultrasoundreturn signals, focused at one or more desired depths.

At 710 a, the ultrasound imaging system transmit beam forms to transmitat least one ultrasound pressure wave along a new first lateral axialray laterally displaced from the new principal axial ray. For example, atransmit beamformer subsystem may produce drive signals to cause atransducer array to transmit ultrasound pressure waves along a new firstlateral axial ray laterally disposed with respect to the new principalaxial ray and focused one or more desired depths.

At 710 b, the ultrasound imaging system receive beam forms to receive atleast one ultrasound return or echo signal in response to the ultrasoundpressure wave transmitted along the new first lateral axial ray. Forexample, a receive beamformer subsystem may filter and otherwise processthe ultrasound return signals to produce image data and to determineinformation (e.g., echo and/or “Doppler” characteristics or parameters)represented in the ultrasound return signals, focused at one or moredesired depths.

At 712 a, the ultrasound imaging system transmit beam forms to transmitat least one ultrasound pressure wave along a new second lateral axialray laterally displaced from the new principal axial ray and the newfirst lateral axial ray to sample at least two additional sample volumesaxially opposed to one another across the new principal sample volume.

At 712 b, the ultrasound imaging system receive beam forms to receive atleast one ultrasound return or echo signal in response to the ultrasoundpressure wave transmitted along the new second lateral axial ray. Forexample, a receive beamformer subsystem may filter and otherwise processthe ultrasound return signals to produce image data and to determineinformation (e.g., echo and/or “Doppler” characteristics or parameters)represented in the ultrasound return signals, focused at one or moredesired depths.

Thus, the ultrasound imaging system may, for example, sample at leasttwo additional sample volumes, laterally opposed to one another acrossthe new principal sample volume. Hence, the ultrasound imaging systemmay, for example, beam form to transmit the ultrasound pressure wavesalong at least three axial rays, the three axial rays laterally spacedfrom one another.

FIG. 8 shows a two-dimensional ultrasound image 800 which may beproduced by an ultrasound imaging system according to one illustratedembodiment.

The two-dimensional ultrasound image 800 (e.g., B-mode image) representsa structure 802, for example a bodily tissue such as an artery. Asillustrated, a region of interest (ROI) 804 may be defined in thetwo-dimensional ultrasound image 800. The ROI 804 may be defined in anumber of manners. For example, an operator may define a desired ROI 804using a cursor and user controls. Also for example, an ROI 804 may bedefined based on certain criteria or characteristics represented in theinformation (e.g., echo and/or “Doppler”) captured by the ultrasoundimaging system.

FIG. 9 shows a method 900 of operating an ultrasound imaging system,according to one illustrated embodiment. The method 900 may, forexample, be executed as part of the method 500 (FIG. 5). The method 900may adjust a location of a principal sample volume or select a newprincipal sample volume selected so as to remain focused on anidentified ROI.

At 902, the ultrasound imaging system selects new principal samplevolume to at least partially coincide with an ROI 804 (FIG. 8) in anobject being imaged.

At 904, the ultrasound imaging system selects additional samplevolume(s) to be sampled that have at least respective portions thereofthat are at least one of axially displaced and/or laterally displacedwith respect to the new principal sample volume.

FIG. 10 shows a two-dimensional ultrasound B-mode image 1000 and atwo-dimensional spectral “Doppler” trace 1002 which may be produced byan ultrasound imaging system according to one illustrated embodiment.Such may be displayed by an ultrasound imaging system operating in anecho/Doppler mode.

The two-dimensional B-mode ultrasound image 1000 represents a structure1004, for example a bodily tissue such as an artery. As illustrated, acurrent principal sample volume 1006 may be defined in thetwo-dimensional ultrasound image 1000. The current principal samplevolume 804 represents a volume currently being sampled at a particularrange of depths.

The spectral Doppler trace 104 represents a distribution of frequenciesin a “Doppler” signal, which may be employed in determining velocity ofa tissue, for example velocity of a bodily fluid such as blood in anartery or velocity of a valve such as a mitral valve in the heart.

FIG. 11 shows a method 1100 of operating an ultrasound imaging system,according to one illustrated embodiment. The method 1100 may, forexample, be executed as part of the method 500 (FIG. 5). The method 110may adjust a location of principal sample volume or select a newprincipal sample volume so as to maintain the principal sample volumerelative to some structure. Such may, for example, allow the principalsample volume to be maintained in the center of an artery 1004 (FIG.10), as the transducer array is moved along the artery while looking forchanges in blood flow.

At 1102, the ultrasound imaging system selects new principal samplevolume 1006 (FIG. 10) to be centered with respect to at least onestructure 1104 (FIG. 10) of an object being imaged.

At 1104, the ultrasound imaging system selects additional samplevolume(s) to be sampled that have at least respective portions thereofthat are at least one of axially displaced and/or laterally displacedwith respect to the new principal sample volume.

The above description of illustrated embodiments, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe embodiments to the precise forms disclosed. Although specificembodiments of and examples are described herein for illustrativepurposes, various equivalent modifications can be made without departingfrom the spirit and scope of the disclosure, as will be recognized bythose skilled in the relevant art. The teachings provided herein of thevarious embodiments can be applied to other ultrasound systems, notnecessarily the exemplary ultrasound imaging system generally describedabove.

For instance, the foregoing detailed description has set forth variousembodiments of the devices and/or processes via the use of blockdiagrams, schematics, and examples. Insofar as such block diagrams,schematics, and examples contain one or more functions and/oroperations, it will be understood by those skilled in the art that eachfunction and/or operation within such block diagrams, flowcharts, orexamples can be implemented, individually and/or collectively, by a widerange of hardware, software, firmware, or virtually any combinationthereof. In one embodiment, the present subject matter may beimplemented via ASICs. However, those skilled in the art will recognizethat the embodiments disclosed herein, in whole or in part, can beequivalently implemented in standard integrated circuits, as one or morecomputer programs executed by one or more computers (e.g., as one ormore programs running on one or more computer systems), as one or moreprograms executed by on one or more controllers (e.g., microcontrollers)as one or more programs executed by one or more processors (e.g.,microprocessors), as one of more PGAs such as field programmable gatearrays (FPGAs), as other firmware, or as virtually any combinationthereof, and that designing the circuitry and/or writing the code forthe software and or firmware would be well within the skill of one ofordinary skill in the art in light of the teachings of this disclosure.

When logic is implemented as software and stored in memory, logic orinformation can be stored on any physical computer-readable medium foruse by or in connection with any processor-related system or method. Inthe context of this disclosure, a memory is a computer-readable mediumthat is an electronic, magnetic, optical, or other physical device ormeans that contains or stores a computer and/or processor program. Logicand/or the information can be embodied in any computer-readable mediumfor use by or in connection with an instruction execution system,apparatus, or device, such as a computer-based system,processor-containing system, or other system that can fetch theinstructions from the instruction execution system, apparatus, or deviceand execute the instructions associated with logic and/or information.

In the context of this specification, a “computer-readable medium” canbe any physical element that can store the program associated with logicand/or information for use by or in connection with the instructionexecution system, apparatus, and/or device. The computer-readable mediumcan be, for example, but is not limited to, an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system, apparatusor device. More specific examples (a non-exhaustive list) of thecomputer readable medium would include the following: a portablecomputer diskette (magnetic, compact flash card, secure digital, or thelike), a RAM, ROM, an erasable programmable read-only memory (EPROM,EEPROM, or Flash memory), a portable compact disc read-only memory(CDROM), digital tape.

The various embodiments described above can be combined to providefurther embodiments. To the extent that they are not inconsistent withthe specific teachings and definitions herein, all of the U.S. patents,U.S. patent application publications, U.S. patent applications, foreignpatents, foreign patent applications and non-patent publicationsreferred to in this specification and/or listed in the Application DataSheet, including but not limited to U.S. Pat. No. 5,893,363 and U.S.Pat. No. 7,604,596 are incorporated herein by reference, in theirentirety. Aspects of the embodiments can be modified, if necessary, toemploy systems, circuits and concepts of the various patents,applications and publications to provide yet further embodiments.

One of ordinary skill in the art will recognize that any one or more ofthe acts or structures recited in any of the dependent claims could beincluded in the independent claim, the remaining dependent claimsdepending off the modified independent claim. That is, while thedependent claims set out specific acts and structures, such acts andstructures may be combined in any combination or permutation.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

What is claimed is:
 1. An ultrasound imaging system, comprising: atransducer array; at least one transmit and receive beamformer forselectively transmitting and receiving ultrasound signals in a desireddirection; a control system configured to: control the transmitbeamformer to generate one or more ultrasound pressure waves on a rayvia the transducer array towards a principal sample volume and one ormore ultrasound pressure waves on rays that are laterally spaced fromthe ray towards the principal sample volume; control the receivebeamformer to receive a number of ultrasound return signals via thetransducer array, the number of ultrasound return signals being receivedfrom the principal sample volume and at a number of additional samplevolumes that are axially displaced or laterally displaced with respectto the principal sample volume; evaluate at least one of a power, avariance, or velocity of the echo data represented in the receivedultrasound return signals originating from the principal sample volumeand from the number of additional sample volumes for a characteristicthat represents a structure of interest; and adjust at least oneoperational parameter of the ultrasound imaging system to select alocation of one of the additional sample volumes to be a location for anew principal sample volume based at least in part on the evaluatedpower, variance or velocity of the received ultrasound return signalsfrom the location of the additional sample volume having acharacteristic that represents the structure of interest; and a displaycommunicatively coupled to the control system to display images of theprincipal sample volume.
 2. The ultrasound imaging system of claim 1,wherein the control circuit is further configured to: control thetransmit beamformer to generate a number of ultrasound pressure wavesvia the transducer array that are directed to the location of the newprincipal sample volume a number of additional sample volumes that areaxially displaced or laterally displaced with respect to the location ofthe new principal sample volume.
 3. The ultrasound imaging system ofclaim 1, wherein the number of additional sample volumes surround thelocation of the principal sample volume in a 2D plane.
 4. The ultrasoundimaging system of claim 1, wherein the number of additional samplevolumes surround the location of the principal sample volume in 3Dspace.